Strange improvement of spark discharge

[exnihiloest]

A capacitive discharge ignition system produces a much better spark with diodes (fig 2B) than the classical one (fig 2A).
Fig 3A is the same principle as 2B but with a gas discharge tube to switch the capacitor.

The question is: why the diodes 1N5408 improve the process? It is not clear.

If there is a negative voltage at the output coil when the capacity is discharged, we see that the diodes turn on, providing current to the primary which should generate a positive voltage in the secondary, against the initial negative voltage. So we should not expect for an improvement of the spark.
And if the output voltage is positive when the capacitor is discharged, then the diodes are blocked, at least until 6*1KV which is the breakdown voltage. May be there is a reverse current but do the diodes act as zener diodes or do their voltage collapses when the maximum reverse voltage is attained?

The picture comes from the paper at http://arxiv.org/abs/1110.0483, which is of poor value from a theoretical viewpoint and also experimental (many tests but not one current measurement, only voltages!), nevertheless the involved phenomena could be of interest for our goal.

Any idea?

[EMdevices]

Hi exnihiloest,  I think I can help explain why the diodes make a difference because I played with this set up many years ago.


the step up transformer is only needed to ionize the gap, which than drops in resistance significantly,  after that, the capacitor can drive current straight through the diodes into the gap, and this current is much stronger and produces a brighter and lauder pop.

With my experiment I got such a burst of energy in such a short time it melted the surface of a physics lab table (hard material) and turned it into glass.   Not even the professors could explain it.  

EM

PS  The spark gap was right next to the table surface, about 1 mm off the surface, and the flash and loud pop left a 2 cm diameter glassy mark on the surface form the intense heat I guess.  I was using a 100 uF electrolitic  charged to about 150 volts,  so about 1 J of energy discharged into the gap in less than 1 us perhaps, I never measured the actual pulse, its just an estimation.

[ion]

EMdevices is right on the mark with his analysis of this one.

That's why spacing is important on mains circuits, so that a momentary lightning arc-over does not create a catastrophic event with thousands of amperes flowing.

In triggerable spark gaps, small initiating discharges create the ionization path necessary for the larger, higher current discharge to follow.

The diodes are actually unneccessary, all that is needed is a wire from the primary placed in the ionization path.

[the_big_m_in_ok]

In triggerable spark gaps, small initiating discharges create the ionization path necessary for the larger, higher current discharge to follow.
...
The diodes are actually unneccessary, all that is needed is a wire from the primary placed in the ionization path.

Precisely.  Radio Shack sells a xenon flash tube that works as ION describes.  Xenon flashers all do, inasmuch as I know.  Since Radio Shack is my only supplier(I only buy a few things a month) the xenon tube should work well for my future projects that need 4,000 VDC to ignite the tube.   EMI should be reduced considerably as well.

--Lee

[MileHigh]

World's Simplest Xenon Flasher

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[wattsup]

These guys seem to know alot about spark gaps.
Lot's of standard specs.
http://www.highenergydevices.com/

wattsup

[exnihiloest]

Hi exnihiloest,  I think I can help explain why the diodes make a difference because I played with this set up many years ago.


the step up transformer is only needed to ionize the gap, which than drops in resistance significantly,  after that, the capacitor can drive current straight through the diodes into the gap, and this current is much stronger and produces a brighter and lauder pop.

With my experiment I got such a burst of energy in such a short time it melted the surface of a physics lab table (hard material) and turned it into glass.   Not even the professors could explain it.  

EM
...

The high voltage/low current of the output coil switches on the ionized channel, and the low voltage/high current of the capacitor enhances the power in the spark gap.
Your explanation is straightforward and fits well the experiment.

So there is likely no ou but if we want to check it, to insure that the effect of the melted surface of the table was compatible with the available energy, it appears that it's difficult, we would need a calorimeter and measure the quantity of heat produced in the spark.

[exnihiloest]

...
The diodes are actually unneccessary, all that is needed is a wire from the primary placed in the ionization path.

Sure. What is astonishing is that I have had this idea a long time ago, then I completely forgot it and I have not even recognized the principle in the paper that I presented here.
Hello memory. Aging is very annoying!   

[ion]

Sure. What is astonishing is that I have had this idea a long time ago, then I completely forgot it and I have not even recognized the principle in the paper that I presented here.
Hello memory. Aging is very annoying!   

Your profile says your age is N/A so you can't use that as an excuse. Wait till you get to be my age LOL.

[the_big_m_in_ok]

Your profile says your age is N/A so you can't use that as an excuse. Wait till you get to be my age LOL.

My birthday is the 8 of Oct.  I'll be 62.   "Senior moments" come more frequently in the last few years.      

--Lee

[the_big_m_in_ok]

Concerning posted Reply #6,

A theoretical question:  How would the radiant energy of a spark gap in a Tesla hairpin circuit, when HV capacitors are used at the bottom of the 2 inputs, be different than without capacitors---and is anything in that regard uniform in presentation between different circuits or even tested to verification?

I admit I have no experimental experience with Tesla circuits, which is why I ask.

--Lee

[EMdevices]

Quote from the paper EX posted up top!

Case Fig.2b: the output HV from the coil for the first sees the ground through the attached diodes, since they are "open", thus starts to flow that path. As soon as the current through the diodes reaches "surge current", its flow is abruptly disrupted by rapid diode shut down. As the next easiest escape path is spark gap, plasma discharge is initiated. With eyes and photo camera there can be observed a big plasma ball around discharge electrodes, also visible that the wire gets kinetic energy – is swinging afterwards. In addition the sound power is higher – louder, well noticeable by hearing.

I can so relate to this.   When I did my experiment years ago in a physics laboratory at school, there were two or three students in the lab and the door was opened to the hallway.  When I initiated the spark,  the flash was so bright and blinding, the wires on the table and the table itself shook, and the boom of the explosion was so loud that everyone thought a bomb went off.    My ears were ringing and the other students were down on the floor out of instinct and professors rushed in to see what had happened.   The wire had been blown apart about 6 inches and melted at the ends where the gap formed,  I estimated they melted back about half an inch.   To this day I don't know why this happened, because I had repeated the experiment a few times afterwards and could not duplicate it.   Something must have lined up just right for this massive explosive arc to occur.    So anyway, I'm glad these guys are exploring these phenomena.  I can't say there is no OU, because I don't have proof, but it sure sounded like there was more energy there, in fact I was not the one to suggest it, the professors were.   They thought I had a firecracker or some explosive that went off.    

By the way, I left out a missing part of this strange experiment.    I had it set up so I can repel two coils apart, like Edwin Gray suggested.   I had a pendulum setup with a meter stick so I can see how far the pendulum with the coil at the end would swing, and calculate the kinetic energy imparted to it.   Than I had a recapture circuit so I can reclaim the kickback from the coil.  I was doing a quantitative experiment to prove to the professors that Edwin Gray may be right, when this unexpected explosion occurred.   And besides,   the coil that were hanging from the structure on a pendulum,  melted their wires as well, but not any of the other wires, which was very odd.   The wires melted inside the coils and broke connection, very puzzling.   they also did not swing out but shook inplace.   So this must be a type of induction kickback phenomena interacting with a plasma arc, in a way that may not be understood fully.  Or maybe it's just a big surge of current occurring in a very short time that does the trick.   So yes, I would like to leave this open as a possibility for OU.   who know, if the impulse is so strong and the temperature so high, who's to say that fusion or fission might not be happening, or some exothermic chemical reaction occurring, like burning metal oxidizing with the oxygen in the air?

EM

[exnihiloest]

@EM

When a big capacitor is suddenly discharged, there is always a big noise and there can be a severe damage in the conductors.
To come out of speculations, the important point is to compute the energy that was available during the experiment. We must know the value of the capacitor, at what voltage it was charged, if the power supply was still connected during the capacitor discharge and how much power it can provide.

[the_big_m_in_ok]

@EM

When a big capacitor is suddenly discharged, there is always a big noise and there can be a severe damage in the conductors. ...

There's something else I learned in the Air Force:  Very Large shorted capacitors have a tendency to explode.  A quote:

"Capacitors are electrical dynamite."
                                --Nicola Tesla

This is a long page attributed to Tesla's quotations, so it might be in here.

http://www.frankgermano.net/teslaquotes.htm

--Lee